1. Field of the Invention
This invention relates to temporary supporting arrangements and more particularly it concerns the stable positioning of heavy structures on or near a water retaining wall, such as a dam wall.
The invention is particularly suited for use in dam reinforcement operations wherein heavy machinery, such as drilling rigs and the like, must be maintained accurately positioned atop a rather narrow dam wall. In dam reinforcement operations holes are drilled down through the entire height of the dam wall and down into the underlying bedrock. Anchor rods are then placed into the bedrock and secured thereto. These anchor rods extend up through the top of the dam wall; and threaded nuts or equivalent means are provided to pull up on the anchor rods to place them in tension while pressing down on the top of the dam wall to place it in compression and to hold it solidly in place. In some cases grout is forced down into the drilled holes.
2. Description of the Prior Art
In the past, dam drilling operations were carried out either by mounting the drilling machinery on the dam wall itself or by mounting the drilling machinery on a barge anchored or moored next to the dam wall. Neither of these two arrangements was satisfactory, however. In the case where the drilling machinery was mounted on the dam wall itself, a problem of stability existed. This occured because the dam wall was usually not of sufficient width to allow the machinery to rest on it without extensive framework support. In the case where the drilling machinery was mounted on a barge it was difficult, due to water movements and changes in water level, to maintain accurate positioning at all times of the drilling machinery with respect to the dam wall during a drilling operation. Steady and accurate positioning of the drilling machinery is necessary to keep the drilled hole straight and plumb and to prevent binding and possible loss of the drilling tool.